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Study of tau lepton decays involving K0S at Belle

DC Field Value Language
dc.contributor.advisor최선호-
dc.contributor.author류수-
dc.date.accessioned2017-07-14T00:55:14Z-
dc.date.available2017-07-14T00:55:14Z-
dc.date.issued2012-08-
dc.identifier.other000000003330-
dc.identifier.urihttps://hdl.handle.net/10371/121484-
dc.description학위논문 (박사)-- 서울대학교 대학원 : 물리·천문학부(물리학전공), 2012. 8. 최선호.-
dc.description.abstractThe τ lepton is the only known lepton massive enough to decay into hadrons via a weak vector current, and this provides a sensitive probe of the standard model parameters,-
dc.description.abstractVus-
dc.description.abstract, αs and ms. However, because of the limited numbers of τ+τ− events, the hadronic decays involving kaons in τ lepton which is directly related to-
dc.description.abstractdetermination has not been well studied for the decades.
The Belle experiment provides the best environments for studying τ leptons because of the high luminosity of e+e− collisions result in the production of large numbers of τ+τ− events. We report measurements of
branching fractions for inclusive/exclusive τ decays involving K0S → π−π+ with 669 fb−1 accumulated data at Belle detector at the asymmetric energy KEKB e+e− collider. The branching fraction measured for the inclusive decay is B(τ− → K0S X−ν ) = (0.910±0.001±0.046)%, where X− can be anything
-
dc.description.abstractfor exclusive decays we report:
B(τ− → π−K0S ν ) =(4.10 ± 0.01 ± 0.21) × 10−3
B(τ− → K−K0S ν ) =(7.09 ± 0.06 ± 0.41) × 10−4
B(τ− → π−K0S π0ν ) =(1.95 ± 0.02 ± 0.11) × 10−3
B(τ− → K−K0S π0ν ) =(7.31 ± 0.12 ± 0.49) × 10−4
We also studied decays involving two K0S:
B(τ− → π−K0SK0Sν ) =(2.41 ± 0.04 ± 0.26) × 10−4
B(τ− → π−K0SK0Sπ0ν ) =(2.06 ± 0.23 ± 0.24) × 10−5
where B(τ− → π−K0SK0Sπ0ν ) is the first measurement. We also report the first observation of the channel τ− → f1(1285)-ν in π−K0SK0Sπ0 decay with its total branching fraction of (1.07±0.23±0.16)×10−5. With these results,
we expect the most precise value of
-
dc.description.abstractcan be achieved.-
dc.description.tableofcontentsContents
1 Introduction 1
1.1 The τ lepton . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1.1 τ pair production . . . . . . . . . . . . . . . . . . . . . 2
1.1.2 Branching fraction . . . . . . . . . . . . . . . . . . . . 3
1.2 Hadronic τ decay . . . . . . . . . . . . . . . . . . . . . . . . . 14
1.2.1 Hadronic decays and their structures . . . . . . . . . . 14
1.2.2 Spectral function . . . . . . . . . . . . . . . . . . . . . 22
1.2.3
-
dc.description.tableofcontentsVus-
dc.description.tableofcontentsand ms . . . . . . . . . . . . . . . . . . . . . . . . 25
1.3
-
dc.description.tableofcontentsand τ decays . . . . . . . . . . . . . . . . . . . . . . . . 27
1.3.1 Cabbibo Kobayashi Maskawa(CKM) matrix . . . . . . 27
1.3.2 Measurements of CKM matrix elements . . . . . . . . 28
1.3.3
-
dc.description.tableofcontentsdetermination in hadronic τ decays . . . . . . . . 31
1.4 Outline of thesis . . . . . . . . . . . . . . . . . . . . . . . . . . 35
2 B-factory 37
2.1 KEKB storage ring . . . . . . . . . . . . . . . . . . . . . . . . 40
2.1.1 Physical requirements . . . . . . . . . . . . . . . . . . 40
2.1.2 Accelerator Design . . . . . . . . . . . . . . . . . . . . 43
2.1.3 Performance . . . . . . . . . . . . . . . . . . . . . . . . 46
2.2 The Belle Detector . . . . . . . . . . . . . . . . . . . . . . . . 48
2.2.1 Extreme Forward Calorimeter(EFC) . . . . . . . . . . 48
2.2.2 Silicon Vertex Detector(SVD) . . . . . . . . . . . . . . 50
2.2.3 Central Drift Chamber(CDC) . . . . . . . . . . . . . . 54
2.2.4 Aerogel threshold Chrenkov Counters(ACC) . . . . . . 60
2.2.5 Time-of-flight Counters(TOF) . . . . . . . . . . . . . . 64
2.2.6 Electromagnetic Calorimeter(ECL) . . . . . . . . . . . 68
2.2.7 K0L and Muon Detection System(KLM) . . . . . . . . . 72
2.2.8 Trigger . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
2.2.9 Data Acquisition System(DAQ) . . . . . . . . . . . . . 79
2.2.10 Computing Systems and Softwares . . . . . . . . . . . 82
2.2.11 Monte Carlo simulation in τ analysis . . . . . . . . . . 85
3 τ+τ− event selection 89
3.1 Pre-selection of τ events . . . . . . . . . . . . . . . . . . . . . 89
3.2 Selection of hadronic τ decays . . . . . . . . . . . . . . . . . . 95
3.2.1 K0S selection . . . . . . . . . . . . . . . . . . . . . . . 99
3.2.2 π0 selection . . . . . . . . . . . . . . . . . . . . . . . . 102
3.2.3 Particle Identification . . . . . . . . . . . . . . . . . . 102
3.2.4 τ− → K0S (particles)−ν events . . . . . . . . . . . . . 105
3.2.5 τ− → π−(K−)K0S ν . . . . . . . . . . . . . . . . . . . 105
3.2.6 τ− → π−(K−)K0Sπ0ν . . . . . . . . . . . . . . . . . . 105
3.2.7 τ− → π−K0SK0S(π0)ν . . . . . . . . . . . . . . . . . . . 107
3.3 Selection of e-μ events . . . . . . . . . . . . . . . . . . . . . . 110
4 Data analysis 115
4.1 Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
4.1.1 The event selection efficiency . . . . . . . . . . . . . . 116
4.1.2 Corrections for the particle ID . . . . . . . . . . . . . . 118
4.1.3 Correction for K0S efficiency . . . . . . . . . . . . . . . 119
4.1.4 Correction to π0 efficiency . . . . . . . . . . . . . . . . 119
4.1.5 Efficiency dependence on hadronic current . . . . . . . 119
4.1.6 Efficiency of Sgg sideband subtraction . . . . . . . . . . 125
4.2 Background estimation . . . . . . . . . . . . . . . . . . . . . . 126
4.2.1 Non-π0 background . . . . . . . . . . . . . . . . . . . 128
4.2.2 Continuum background . . . . . . . . . . . . . . . . . 131
4.2.3 Background from τ− → π−K0SK0Lπ0ν decays . . . . . 132
4.2.4 Summary of the background . . . . . . . . . . . . . . . 133
5 Determination of the branching fractions 139
5.1 Method of branching fraction calculation . . . . . . . . . . . . 139
5.2 The branching fraction measurement . . . . . . . . . . . . . . 140
5.2.1 For inclusive decay . . . . . . . . . . . . . . . . . . . . 140
5.2.2 For the decays with one K0S . . . . . . . . . . . . . . . 141
5.2.3 For the decays with two K0S . . . . . . . . . . . . . . . 146
6 Systematic uncertainties 153
6.1 Uncertainty from the normalization . . . . . . . . . . . . . . 154
6.1.1 △Be and △Bμ . . . . . . . . . . . . . . . . . . . . . . . 154
6.1.2 △ǫe-μ contribution . . . . . . . . . . . . . . . . . . . . 155
6.1.3 △Ne-μ and △Be-μ . . . . . . . . . . . . . . . . . . . . 156
6.1.4 Luminosity . . . . . . . . . . . . . . . . . . . . . . . . 157
6.2 Uncertainty from background estimation . . . . . . . . . . . . 157
6.3 Uncertainty from efficiencies . . . . . . . . . . . . . . . . . . . 158
6.3.1 Tracking efficiency . . . . . . . . . . . . . . . . . . . . 159
6.3.2 Charged pion/Kaon ID efficiency . . . . . . . . . . . . 159
6.3.3 K0S
efficiency . . . . . . . . . . . . . . . . . . . . . . . 159
6.3.4 π0 efficiency . . . . . . . . . . . . . . . . . . . . . . . . 160
6.3.5 Dependency on hadron model . . . . . . . . . . . . . . 160
6.3.6 Trigger efficiency . . . . . . . . . . . . . . . . . . . . . 161
6.3.7 Effect from γ veto . . . . . . . . . . . . . . . . . . . . . 161
6.4 Summary of systematic uncertainty . . . . . . . . . . . . . . . 162
7 Conclusions 165
A π0 efficiency study using τ− → π−π0ν 177
A.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177
A.2 Event selection . . . . . . . . . . . . . . . . . . . . . . . . . . 180
A.2.1 Data sample . . . . . . . . . . . . . . . . . . . . . . . . 180
A.2.2 Selection Criteria . . . . . . . . . . . . . . . . . . . . . 180
A.2.3 The general features of τ− → ππ0ν candidates . . . . 182
A.3 Branching ratios and Efficiency corrections . . . . . . . . . . 186
A.3.1 For single ππ0 event . . . . . . . . . . . . . . . . . . . 186
A.3.2 For double ππ0 event . . . . . . . . . . . . . . . . . . . 187
A.4 Systematic Uncertainty . . . . . . . . . . . . . . . . . . . . . . 194
A.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197
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dc.formatapplication/pdf-
dc.format.extent16462105 bytes-
dc.format.mediumapplication/pdf-
dc.language.isoen-
dc.publisher서울대학교 대학원-
dc.subjecttau lepton-
dc.subjecthadronic decays-
dc.subjectVus-
dc.subjectBelle-
dc.subject.ddc523-
dc.titleStudy of tau lepton decays involving K0S at Belle-
dc.typeThesis-
dc.description.degreeDoctor-
dc.citation.pages227-
dc.contributor.affiliation자연과학대학 물리·천문학부(물리학전공)-
dc.date.awarded2012-08-
Appears in Collections:
College of Natural Sciences (자연과학대학)Dept. of Physics and Astronomy (물리·천문학부)Physics (물리학전공)Theses (Ph.D. / Sc.D._물리학전공)
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